Oriented and partially dehydrated samples of bacteriorhodopsin will be analyzed for transient changes in the infrared spectral region during photocycling. Single-beam optics and signal averaging/computer analysis will be utilized. The data will reveal changes in the protonation state of Schiff-base, tyrosine, carboxyl and amino groups, as well as peptide oxygens during the photocycle. Information about helix distortion, pigment conformation and water binding is also anticipated.